Assessment Effect of the Spatial Resolution of Digital Elevation Model on Daily Discharge Estimation of Arazkuseh Watershed Using SWAT Model

The spatial quality of the Digital Elevation Model (DEM) has a great effect on the Soil and Water Assessment Tool (SWAT) semi-distributed model. The purpose of this study was to evaluate the effect of spatial accuracy of three DEMs with spatial resolutions of 10, 50 and 200 m on the results of daily discharge simulation in the Arazkuseh subwatershed located in Gorganroud watershed, Golestan province, Iran. To do this, after-mentioned DEMs was obtained.  First, the model was run using a DEM with a spatial resolution of 10 m and climate data from 1998 to 2013. So that 1998 to 2000 were used to warm-up the model, 2001 to 2009 to calibrate and 2010 to 2013 to validate the model. In the validation period, the results of coefficient of determination ranged from 0.40 to 0.60 and Nash-Sutcliffe efficiency criteria ranged from 0.37 to 0.58. Both criteria had a decreasing value in the validation phase compared to the calibration phase. The PBIAS criteria was negative for DEMs with 10 and 50 m spatial resolution, respectively which indicates overestimation, and positive value ​​for DEM with 200 m spatial resolution, which represents the overestimation of the model. The results showed that the spatial resolution of 50m is the best spatial resolutions to simulate the discharge on a daily time scale for Arazkuseh watershed.